The Hohentwiel Fortress Ruins cover more than 22 acres (9 ha) on the volcanic rock of the same name. Not only is the exposed location striking, the eventful history of the castle since the 5th century BC is also impressive. Beginning in the Neolithic period around 5,000 BC, settlers, farmers and stock breeders left their traces at the base of the Hohentwiel.
However, proof of a settlement higher up on the mountain comes much later. In 914 Swabian nobles founded the castle on Hohentwiel, which King Konrad I futilely besieged in 915. Already at that time the fortress on Twiel Mountain proved its stability often put to the test over the centuries which followed. In the course of the 10th century Duke Burkhard III expanded Hohentwiel to an important center of power. St. Georg Monastery, located within the fortress, goes back to its founding, which was energetically brought to completion by Burkhard's widow, Duchess Hadwig.
With the mountain monastery Hadwig not only supported cultural and religious life, she also strengthened the political influence of her noble family. Following Hadwig's death in 994, Emperor Otto III broke the influence of this center of power which opposed the Reich and his successor King Heinrich II moved the monastery to Stein am Rhein in 1005. As a result, the Swabian dukes lost their influence at Hohentwiel forever.
In the 19th century, Joseph Viktor von Scheffel created a much-regarded literary monument to the well-educated Duchess Hadwig with his novel "Ekkehard".
In the 11th century Hohentwiel was marked by the conflicts of the Investiture. The dukes of Zähringen, who were now in possession of Hohentwiel, supported Pope Gregor VII, who deprived the Emperor of the right to appoint the bishops (so-called Investiture). However, in 1086 the Abbot Ulrich von St. Gallen came into possession of the castle for well over a quarter of a century until the Zähringer were able to gain control of Hohentwiel in the 12th century again.
When the "Herren von Singen" (Lords of Singen), who from then on called themselves "von Twiel", took charge of the castle, Hohentwiel lost its political influence once and for all in 1122. Not until 1300 did a powerful noble family come to power again at the fortress. The "Herren von Klingenberg", who were allied with the Hapsburgs, purchased the castle. This family with many branches met with its decline due to family quarrels and its disastrous political orientation towards both the Württemberg and the Austrian side.
When ousted in 1519, Duke Ulrich von Württemberg was received at Hohentwiel by Hans Heinrich von Klingenberg. He took up residence there and drove his servant from the castle, which legally belonged to Württemberg since the contracts of 1521 and 1538.
A great deal of what remains of Hohentwiel today can be traced back to its expansion to the state fortress under Duke Ulrich. The oldest realistic representation of the fortress dates from this time, and was produced in 1591 by the ducal architect Heinrich Schickhardt.